Emergency stop operators are used in connection to electric machines for the purpose of actuating one or more contact blocks that control the flow of electric current through such machines. The contact blocks define switches or breakers. Normally, the emergency stop operator comprises a handle by means of which an actuator body in the operator is pushed in a direction towards the contact block in order to generate the breaking of an electric circuit through a displacement of individual contacts in the contact block.
Prior art includes operators in which the actuator body is spring loaded and provided with a latch means formed by a pin that, once the actuator body has been pushed to an active position, such as the initially defined second position, will abut an abutment surface of a sleeve that guides the actuator body and is fixedly attached to the contactor block. The pin may be spring loaded and the abutment surface thereof, or the abutment surface of the sleeve, may be inclined such that the pin will be depressed and will pass the abutment surface upon a given counterforce from the contact block. Accordingly, the actuator body may accidentally return to its first, inactive, position if the counterforce exerted by the contact block is large enough. This is a drawback of this type of operators, since the spring-loading of the pin must be adapted to the different counterforce that may exist depending on the type and number of contact blocks acted upon by the operator.
In order to remedy such drawbacks prior art includes a design as initially defined in this application. According to the teaching of this prior art the second part of the actuator body is a so called gear ring, provided with a plurality of inclined abutment surfaces arranged so as to engage with corresponding abutment surfaces on the inner periphery of the holder element. The gear ring is free to rotate in relation to the first part of the actuator body. The first part of the actuator body is in direction contact with the contactor block. The gear ring is able to slide longitudinally along a central part of the first part of the actuator body. The abutment surfaces of the gear ring and the corresponding abutment surfaces of the sleeve are arranged such that, upon displacement of the actuator body from the first to the second position, and provided that there is a counter pressure from the contact block, the gear ring will be moved to a position in which it rides on a first abutment surface and rotationally moves to a position in which it is located in a stable abutting position, thereby preventing itself and the first part from moving back towards the first position. Each abutment surface of the sleeve is formed as a double cam. Upon a further pushing of the actuator body in the same direction, though from the second position, the gear ring will move in the longitudinal direction in relation to the sleeve abutment, will pass a top of the latter and will slide down the abutment surface of a second cam thereof, thereby rotating slightly, and will eventually go free from the double-cam abutment and will be able to return to the first position.
Prior art also include solutions in which there is required a rotation of the handle in order to achieve the requested result.
However, the above-mentioned kind of double push manoeuvring of the actuator body, and the handle, of this emergency operator of prior art in order to activate and deactivate the operator may be found somewhat illogical. It would be more logical to simply push the handle, or button, connected to the actuator body in a straight rectilinear direction in order to activate the actuator, and to pull back the button or handle in a corresponding opposite rectilinear direction in order to deactivate the actuator.